1. Field of the Invention
This invention relates to improvements in near-infrared quantitative measurements instruments and particularly to a novel NIR quantitative measurement instrument capable of measurements in both reflectance and transmission modes.
2. Prior Art
In the early 1970's, quantitative near-infrared (NIR) instruments were introduced to satisfy the need for rapid accurate measurements of nutritional constituents within grain and oil seeds. In the fifteen or so years since their introduction, near-infrared instruments have proven their ability to provide fast, accurate measurements of protein, oil, moisture and other constituents in a wide variety of these applications. The capability of these instruments have led to their widespread use in qualitative control functions in the grain industry. Specifically, thousands of these instruments are currently used in measuring protein and moisture in wheat and barley.
There are two general types or categories of near-infrared instruments currently on the market: (1) those that make measurements by reflecting light off of a ground sample, and (2) those that make measurements by transmitting light directly through an unground sample. Thus, these instruments act in the reflectance and the transmission modes respectively.
Certain available commercial instruments have the ability of changing from a reflectance measurement mode to a transmission measurement mode but only by making hardware modifications which are both time consuming and subject to operator error.
Furthermore, in the measurement of certain types of products, e.g. mixed feed, forages, or whole grains, measurement of a very large sample is desirable to average out the non-homogeneous content of the sample. In the known commercial instruments the methods used to measure large ground samples include the use of a spinning sample cup which is located eccentrically relative to a light beam, i.e., the NIR optical axis. This approach allows the NIR beam to illuminate a larger area as the cup is rotated. However, in instruments having a rotating sample cup, it is difficult to remove it in order to convert the instrument to a transmission measurement mode which many users prefer for whole grain measurement. There is a significant need in the art to make both transmission and reflectance measurements at multiple positions of a sample without any hardware modifications whatsoever.